Add lock annotations to the header files of our threading libraries.

This change extends all of the functions present in the <pthread.h> and
<threads.h> headers to have lock annotations. This will allow Clang to
warn about the following:

- Locking a function twice,
- Unlocking a function without a mutex being locked,
- Forgetting to unlock a mutex before returning,
- Destroying or reinitializing a mutex that is currenty locked,
- Using an unlocked mutex in combination with a condition variable.

Enabling these annotations already allowed me to catch a bug in one of
our userspace tools (r270749).

1 files changed, 18 insertions, 9 deletions

diff --git a/lib/libstdthreads/threads.h b/lib/libstdthreads/threads.h
index aba9ca13df3c..6f322a5af13e 100644
--- a/lib/libstdthreads/threads.h
+++ b/lib/libstdthreads/threads.h
@@ -79,15 +79,24 @@ int	cnd_broadcast(cnd_t *);
 void	cnd_destroy(cnd_t *);
 int	cnd_init(cnd_t *);
 int	cnd_signal(cnd_t *);
-int	cnd_timedwait(cnd_t *__restrict, mtx_t *__restrict,
-    const struct timespec *__restrict);
-int	cnd_wait(cnd_t *, mtx_t *);
-void	mtx_destroy(mtx_t *);
-int	mtx_init(mtx_t *, int);
-int	mtx_lock(mtx_t *);
-int	mtx_timedlock(mtx_t *__restrict, const struct timespec *__restrict);
-int	mtx_trylock(mtx_t *);
-int	mtx_unlock(mtx_t *);
+int	cnd_timedwait(cnd_t *__restrict, mtx_t *__restrict __mtx,
+    const struct timespec *__restrict)
+    __requires_exclusive(*__mtx);
+int	cnd_wait(cnd_t *, mtx_t *__mtx)
+    __requires_exclusive(*__mtx);
+void	mtx_destroy(mtx_t *__mtx)
+    __requires_unlocked(*__mtx);
+int	mtx_init(mtx_t *__mtx, int)
+    __requires_unlocked(*__mtx);
+int	mtx_lock(mtx_t *__mtx)
+    __locks_exclusive(*__mtx);
+int	mtx_timedlock(mtx_t *__restrict __mtx,
+    const struct timespec *__restrict)
+    __trylocks_exclusive(thrd_success, *__mtx);
+int	mtx_trylock(mtx_t *__mtx)
+    __trylocks_exclusive(thrd_success, *__mtx);
+int	mtx_unlock(mtx_t *__mtx)
+    __unlocks(*__mtx);
 int	thrd_create(thrd_t *, thrd_start_t, void *);
 thrd_t	thrd_current(void);
 int	thrd_detach(thrd_t);